Many styles of present day markers aid in nighttime navigation for drivers along the roadways. Some are passive devices such as raised pavement markers and roadside reflectors. Active markers exist that illuminate in the presence of unsafe road conditions. Additionally, there are devices and methods for detecting the presence of foggy conditions, and providing aid in vehicle navigation by marking the roadway edges. Some systems provide a warning light to illuminate if an IR beam transmission between a transmitter and receiver is disrupted by the presence of fog. The conventional art for roadside illumination is well documented, with systems that cause an action to occur when a break in a beam is sensed. Such systems generally use an optical or IR transmitter on one end of the link, and an IR detector as a receiver on the other. Also included are “stand-alone” fog detection inventions that, rather than sensing a break in a beam, instead transmit a beam outward and sense a reflection off of the fog.
In U.S. Pat. No. 5,554,972, a perimeter warning system is presented in which an alarm is sounded if the continuity of a beam is broken. Additionally, warning systems have been developed to alert drivers to wildlife breaking the perimeter of a roadway, as shown in U.S. Pat. No. 8,410,941, where a break in a transmitted laser beam indicates that animals, such as deer, may be wandering into vehicular traffic areas.
Other systems use solar energy and marker devices in a network. In U.S. Pat. No. 9,142,130, a road safety device uses sound activation to illuminate a warning lamp. Additionally, solar energy is used to power a controller for detection of fog, and activate a plurality of wireless fog lamps, as disclosed in patent publication CN201412765.
In U.S. Pat. No. 7,235,786, a sensor for detecting fog-like media uses two emitted light beams and a receiver to determine the presence of fog through a process of reflection. Methods for utilizing optical or IR reflection of the marking device are also used to determine the presence of fog such as in patent CA1297085.
Until now, however, no easily deployable, low-power devices have been capable of providing a warning indication of pockets of poor visibility along a length of roadway that are self-contained transceivers.